The expression “a final control element for a motor vehicle” means any element that is arranged such that it can move in a motor vehicle and be driven, moved, opened or closed by a motor with respect to a stationary part of the motor vehicle, such as the car body. A final control element represents, for example, the windows or windshields, electrically operable doors (e.g. a tailgate), a sliding roof or a motor vehicle seat.
A motor that is driven electrically is used for operation of the final control element. When the final control element is operated, one problem that arises is that an obstruction may be unpredictably located in the actuating movement of the final control element. Jamming such as this must be detected reliably, particularly where the obstruction is a human body part, and appropriate countermeasures must be initiated, such as stopping or reversing the motor.
By way of example, in order to detect jamming, it is known for a sensor element to be used to detect a parameter that characterizes the motor during the operation of the final control element, and to deduce jamming if there is a discrepancy in comparison to normal operation. For example, DE 10 2005 000 753 A1 discloses the torque of the motor, or a signal that is correlated with the torque of the motor, being recorded over the adjustment range of the final control element and for jamming to be detected if the recorded signal or torque exceeds a response threshold. In this case, provision is made in particular for the response threshold to be instantaneously adapted during the adjustment of the final control element, with an increasing time or spatial change in the correlating signal being taken into account.
An adjustment device having a learning capability such as this can admittedly prevent incorrect reversal of the motor, particularly in the event of aging of the system. However, it disadvantageously does not preclude incorrect reversal in the event of brief operation with a change in the freedom of movement of the drive.